Field of the Invention
The present invention relates to a semiconductor manufacturing method and a semiconductor manufacturing apparatus for forming a contact electrically connecting an n-type region and a p-type region formed in a semiconductor substrate with a metal layer.
Description of the Background Art
Establishing semiconductor-metal ohmic junctions (contacts) is an important technique in the manufacture of semiconductor devices. As a method for forming a contact to a semiconductor substrate formed of silicon carbide (SiC) and the like, a method of depositing a metal material on a heavily-doped impurity region, and then performing heat treatment referred to as post-deposition annealing (PDA) to form a reaction layer is widely known. In the process of manufacturing semiconductor devices, heat treatment is performed for a variety of purposes other than contact formation, for example, for activation of implanted impurities (see US2011/0018005).
A typical example of conventional heat treatment is heating performed for about a few minutes in a furnace, as disclosed in US2011/0018005 and other documents. Heat treatment of rapidly heating a semiconductor substrate for about a few seconds with a halogen lamp and the like is also common.
Depending on the type of heat treatment, however, a longer treatment time, even if it is only a few seconds, can deteriorate other characteristics of a semiconductor device. For example, in heat treatment for forming a contact to an SiC semiconductor substrate, a higher heating temperature is preferred as contact resistance decreases with increasing heating temperature. An SiC semiconductor, however, has been hydrogen-terminated to improve interface characteristics of a gate oxide film, and, when the SiC semiconductor is heat-treated at a high temperature for a few seconds or more for contact formation, hydrogen taken in the vicinity of the interface is desorbed, resulting in deterioration of the interface characteristics. It is difficult to heat treat aluminum, which is used as a metal layer to form a p-type contact, at a high temperature in the first place as aluminum is a low-melting metal.
Heat treatment for activating impurities is typically performed after implantation of the impurities and before formation of a metal layer. When such heat treatment is performed at a high temperature for a few seconds or more, however, the implanted impurities disappear due to out diffusion, and the impurity concentration decreases near the surface of the impurity region, making it difficult to obtain a low contact resistance.